All great points. My point was no one can tell him accurately how much the cost/HP gain is going to be. In other words, the VALUE based on his application. It's just a 383.

Yeah, in the racing world it does matter, that's why real race cars are not using 23* heads anymore to get the flow up.. Porting and flow provide much bigger gains on much bigger setups. More flow has more impact when the entire setup is made to accept it. We're talking about HIS setup. So let's not confuse the issue. As the OP asked.....how much do I have to spend to gain how much DEMONSTRATED GUARANTEED HP? Reasonable question... no question more flow is more HP. The problem is quantifying that. Or maybe it isn't....I don't know. Tell me if it isn't. I can learn something here.

 

SO is this a TBI style injection setup? what exactly are you using on the top of this motor??

 

I don't think its always easy to tell a person how much additional HP they will get based upon cylinder head flow..... in the racing sector with guys running good flowing 23 degree cylinder heads or 18/15 degree, they will typically tell you that for every cfm you find, you'll get 2 HP as your reward if everything else is working right..... and I think many do see this.

Naturally, that does not necessarily apply to a street/strip motor.....typically less.... its a variance based upon every motor..... if a motor has a bottleneck such as a stock tpi or even superram, the additional airflow may only be equal to a fraction of a hp for every cfm...... in some cases, I can see going from a cylinder head that flows 240 cfm to 280 cfm and they only see a 10 hp gain...... but the overlying effect is that even if its just at one spot in the torque curve, you will almost always have more power.......additional airflow will give you more power 9 out of 10 times...... and that 10th time they have other severe bottleneck problems.

But, if two cylinder heads are in the same price range.... and similar runner sizes, and similarly equipped quality valvetrain springs/valves/retainers...... buy the one that flows more air.... it is without a hint of a doubt the cylinder head that is better.

With the poster in this thread, I just noticed he has an 84 crossfire with the X-ram manifold..... I have heard of that manifold, but wouldn't know one if you hit me over the head with it, thus I can't really comment on what its limitations are.... but, I can say, if its anything like the Superram, I think any flow up to around 260-270 cfm will be flow turned into serious HP...... once you get above that, your gains per additional cfm will be considerably limited.... due to the SR limitations, but even then they would see better performance with additional flow, it just would be more subtle improvements.

At least thats my opinion based upon racing my own 383 C4 and observations and countless conversations with other racers here and elsewhere.

I look forward to hearing about your results when you're done !!

later
Beach

 

Hey they are great heads, but saying you don't "need" high flowing heads because your cam will not be too wild is just not true. All things being equal on the head, the more CFM you can get out of it, the more power ANY cam will make.

Is it worth the extra HP? Don't look at it like that. Look at it in the sense that now to achieve your original HP goals you can run less cam making the car more drivable, better on gas etc etc.....wouldn't you say that's worth it? Did GM say: "Well the LS7 is just running a baby smooth idle emissions cam and not a big lumpy race cam so we don't need big CFM"

Nope.

Try 360CFM
Tell you what. Why don't you tell me why the extra cubes is worth the money yet the extra CFM in the heads is not?

A 355 with a killer top of the line head on it will have a far greater potential to perform better than a 383 with a "bargain" head.

I've personally seen hundreds of combos working at a shop with a chassis dyno and I can tell you this: You're first priority is to get the best cylinder head you can, end of story. After that figure out if you can afford the exotic rods, crank, extra cubes etc but NOT the other way around unless you're spraying over 200HP.

 

Crossram intake used?
Not sure you can utilize a big head with that one.
Anyone have info on a real good flowing Crossram after porting (Im assuming youre going to)

 

 

I "think" the X-ram is an aftermarket crossfire manifold that flows fairly decent (It might just be a heavily modified stock manifold, but not sure)

Regardless, it is aftermarket, thus I gotta believe that means its a big step over the stock crossfire manifold or at least I hope so.....

 

Looks like its a bolt on top for it only.
Wheres all our Crossfire junkies?

 

i havent seen any combos using a cross fire type intake. good luck with that, i'd be curious as to how it turns out

 

"The base manifold is a race proven 360-degree low profile street ram. Originally designed by WEIAND and now built by Holley"(taken from xrams site) with an alluminum type plates on top for the tb mounting. Sorry I don't know exactly what to call that part. Once boring out the TB's and changing injectors to even 90lb that gives you 180lbs/hr

I have already seen and read about CFI's making over 400hp/460tq. Whether thats at the crank or rear wheel I'm unsure.

There is even the offy crossram available out there that can be used. The amount of air/fuel needed for a 383 build is no different than any other. Here again I'm not concerned about fuel delivery.
Sizing of the head/cam is more critical for me than fuel.

 

Hmm, intersting. What was the name of the product guys used to use on top of the stock Crossfire base?
How difficult would this be to tune?

Anyone have a pic of this Xram without the top on it? Curious.

 

Here you go.

Then it has the aluminum plenom on top for the tb's. Very simple. This is what I was looking for http://www.holley.com/7547-1.asp
Tuning is no problem. I have the ebl/flash ecm for mine. No chip burning, and even does some self VE learns. And tune using TunerPro.
This graph is old but might give you an idea of what the car was doing to first time I ran with the new ecm.

 

True, that's why Deakins points out the best way to achieve that is to buy bare castings and believe it or not, HAND PORT THEM. People who are really **** about getting the most power do that. It is the engine builder's position that hand porting can really get you where you want to go and is superior to a CNC port. Now, although a CNC port is more consistent, it is not the method which yields the most power for the specific build.

I'm sure that's what you meant.

 

Nothing is more accurate or repeatable than CNC porting. Even at that there can be a small percentage of varaition but nothing is perfect.
Most CNC programs are modeled after what one may feel is the "best" hand port job they could muster. Being as there is too much time involoved a CNC is the only way they can really sell the head reasonably and have it perform well.
To take an "as cast" and have the option of doing bowls, exh, or not doing another part isnt a bad thing. Most porters hate selling CNCed heads as theres really no money fopr them to be made, 99% of the time they will steer you towards something that they are grinding on and say all the right things to lead you to believe youre getting the same thing for less. Dont believe it.

Id like to see more on this build sounds interesting;something different.

 

There really is no difference than hand porting vs CNC, except the CNC is more accurate as noted. For CNC porting, what they do to create a program for a particular cylinder head is first they port/flow test a chamber thoroughly by hand..... once they are happy with the desired results of the port as per the flowbench, they put the cylinder head on a CNC machine equipped with a Renishaw Probe system that allows them to digitize the port utilizing a probing auto cycle that will sweep the port in the direction they plan on machining the port...... this creates your xyz coordinate tool path, they then massage the code with the appropriate G, M, F, S & T codes either at the CNC or they send to offline cad/cam software such as Mastercam or Virtual Gibbs...... and they now have a working CNC program..... I teach customers to use this as a subroutine and step over for each chamber and call the sub, but its also important for them to find the next chamber also utilizing a probe system to maintain accuracy from port to port, which can be off due to part fixture skew and even casting in-accuracies. Some will use a pattern repeat cycle and mirror imaging G-code featuers as well.

My point, a CNC porting program is only as good as the initial hand porting.... but once its done and done right, you can't beat the CNC, provided the CNC machine is accurate and the operator is utilizing accurate offsets from hole to hole....

A CNC machine is easier for porters once they have the initial port finished and digitized, all they have to do is mount the cylinder heads on the table and press cycle start versus the alternative of hours with a grinder in hand. However, a good 5 axes VMC with a tilting rotary table is easily over $ 100,000 and for some of the higher quality European and Japanese machines can approach double that..... hence why the big expense for CNC ported cylinder heads.

 

Heheh, is every thread on an engine build going to turn into a cylinder head discussion? The OP fairly clearly stated he was set on what heads he was going to use.

A buildup around the Crossfire/xram should be pretty cool!

 

Thanks, I'm looking forward to doing this as well.
I did call Brodix today...they did suggest either the 200 or 210 for the 383, and also suggested the 200 for a 350. Well I guess you could but anyways.
I did download comps cam selection software and it recommends either the 268XFIHR13 or the 280XFIHR13.
If thats the case the 280 lift I believe is to much for the ik200 heads so I think the springs would have to be changed out.
I am gonna keep and open mind about head selection and really start comparing the pricing of what I want on the other brands as well. Gonna have to look again but I believe the lift on AFR and Dart Pro 1 was .600 and if its gonna cost me an additional 300 for the brodix for porting/springs etc I just may go with one of the others.

 

AFR does have good valve springs out of the box. should match up ok with XFI lobe. if you do use the 280 xfi i'd get AFR's 100 buck optional performance spring which is much better suited to those XFI lobes

Else consider the XE grinds 230/236 with 1.6 rockers, that should make decent power. Tighten it up on a 110lsa and tune it well it should be a nice cam.

Crane/lunati have a few decent grinds as well that should fit your bill

 

Jsup....did you hand port your heads? Where can I get information on this? I have a spare set of 643 LT1 heads I can practice on.

 

I ran the 280XFI with the 8019 AFR srings you're talking about and a 1.7 rocker yet I could rev clean to 6500RPM. Pretty impressive considering allot of people are having problems reving the XFI lobes past 6200 even with 1.6 rockers and the beehive springs they were designed for.

I think the real trick is not the spring pressure of those 8019s but the combined spring pressure and light weight valvetrain that comes with the Comp Port Eliminators.